Rhinomcp.rhp initialization failed - Rhino 8 SR29 Windows 11

Rhino AI
1

Hi everyone,

I’m trying to connect Claude AI to Rhino 8 using RhinoMCP but the plugin won’t load.

My setup: - Rhino 8 SR29 (8.29.26063.11001) - Windows 11 (10.0.26200.0) - .NET SDK 8.0.419 installed - Visual C++ 2015-2022 Redistributable already installed - Python 3.9.13 installed - uv/uvx installed and working

What I tried: - Installing via Package Manager (rhinomcp v0.2.1) - Installing via yak.exe from PowerShell - Dragging rhinomcp.rhp directly into Rhino - Running Rhino as Administrator - Uninstalling and reinstalling multiple times

The error I always get: “Unable to load rhinomcp.rhp plug-in: initialization failed” The Details button shows no useful information.

The uvx rhinomcp server works fine in PowerShell, so the Python side is working correctly.

Any help would be greatly appreciated!

4

Same issue here, confirming this is still happening on the latest stable release, not just a beta build.

Setup: Rhino 8 SR34, Windows. Tested with “Rhino MCP Platform” via Yak Package Manager:

  • Beta 0.2.1-wip — fails
    • Latest stable 0.1.5 — fails identically
  • Exact error: “Unable to load the RhinoMcpPlatform.rhp plug-in: initialization failed.” The Details button shows no useful info, same as reported above.

I also checked Task Manager for lingering rhino-mcp-router.exe processes in case of a port conflict — none found, so that’s ruled out on my end too.

Would love to know if there’s a known fix, or if this needs a proper bug report to the dev team. Trying to use this for a Grasshopper + Claude workflow for chocolate mold design. Happy to share more logs if it helps.

5

Can you post your SystemInfo?

I suspect you’re running net48

6

Hey Callum, hope all good? I’m running into the same wall, “initialization failed” , and can add some data points:

  • Confirmed on Rhino 8, fully updated to latest release — not a stale Rhino build.
  • Fails identically on both 0.1.5 (stable) and 0.2.1-wip, ruling out a version-specific regression.
  • Fails identically whether installed via yak install, Rhino’s built-in Package Manager, or manually dragging the .rhp into the viewport.
  • dotnet --list-runtimes confirms .NET 8 Desktop Runtime is installed (8.0.2, 8.0.30, plus 9.0.19 and 10.0.11) — so guess it’s not a missing-runtime issue.
    Could it be a dll dependency issue?

Thanks in advance!

7

What is your Rhino version?

8

(8.34.26223.11001, 2026-08-11)

9

I get this too:

[PackageManager] Removing inactive version: Rhino-MCP-Platform/0.2.1-wip
[PackageManager] Something went wrong cleaning up Rhino-MCP-Platform/0.2.1-wip: Access to the path ‘e_sqlite3.dll’ is denied.

But I think that is just the connector keeping it running.

10

Yes likely so, you’ll need to close any AI Agent using it before uninstalling